In The Lord of the Rings: The Two Towers, at Helm's Deep when Aragorn was commanding the Elves during the battle, he yells "Ladders" in the Elvish tongue (Sindarin). A moment later we hear Gimli saying "Good", because he was very eager to fight, and finally the wait was over.

all right. +1. is point 1 really true? also elves came to help Rohan just before the battle they wouldn't have discussed about Elvish in battle strategy. Gimli hated elves, so he wouldn't have learned Elvish from Legolas. He must've heard it from Eragon. right
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Hussain TamboliOct 20 '12 at 9:37

I have no idea if ladders sounds similar in both languages but it could be. Both races are similar in age and have not always hated each other. Some words might have crossed over in the time they were still working together (see this for their relationship). As for Gimli, by the time they are in Helm's Deep, he and legolas are already friends.
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OriginOct 20 '12 at 10:08

great link. thanks. I haven't read the books, seen movies lot of times though. Great stuff the link has.
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Hussain TamboliOct 20 '12 at 10:26

1

@Origin It may be possible. But even if the dwarven language was not worked out as accurately as the two elven languages the few examples shown throughout the books suggest that those languages are very different. But I may just have overseen something or might not remember everything.
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Tom Cody♦Oct 20 '12 at 13:20

At the start of the battle, Aragorn led the elf warriors, and he did so using the elvish language. They were all in a group on the wall, and this was where Gimli was. It stands to reason that in preparation for the battle, anyone who was in that group would be briefed on the various commands that Aragorn would use. So I'd argue that off-camera Gimli was told what the various elvish words were and their meaning, so he would be able to follow the same orders as those around him.